This invention relates to reproducing apparatus for magnetic tape and particularly to such apparatus for use in commercial radio broadcasting where it may be required to operate continuously with the highest possible standards of reliability and durability.
Typically, such apparatus is selectively operable in at least three basic modes, namely: play, fast forward and fast rewind.
In play mode, forward and rewind reels are urged in opposite directions by torque motors to tension the tape, a tape lifter lowers the so-tensioned tape onto the reproducing head, and a pressure roller presses the tape into frictional driving engagement against a capstan to move the tape in a forward direction at a lineal play speed determined by the rotational speed of the capstan. When conventional reproducing apparatus is in play mode the torque motors are simultaneously energized through individual relatively large resistors to limit their respective torques to values just sufficient to provide the tape tension required. Continuous operation in play mode causes these relatively large torque-limiting resistors to generate and build up heat within the cabinet. This is objectionable and often requires design compromises in the form of special venting arrangements or blowers to keep the temperature in the cabinet within tolerable limits.
In either fast mode, only the appropriate forward or rewind torque motor is energized, the tape lifter lifts the tape clear of the head, and the pressure roller is held away from the capstan to free the tape from the capstan and enable the tape to be moved at full fast speed determined by the speed of the energized torque motor and the diameter of wrap on the reel of the energized motor. The other torque motor is non-energized, allowing its associated reel to pay off tape freely. The conventional torque-limiting resistors referred to above, will generally be by-passed during either fast mode because no hold-back tension on the tape is required.